This application is based on Japanese Patent Application No. 2000-322353 filed on Oct. 23, 2000, the contents of which are incorporated hereinto by reference.
1. Field of the Invention
The present invention relates to a nozzle-mounting device for removably mounting, on a nozzle holder, a suction nozzle arranged to hold an electric component (typically, an electronic component) by suction under a negative pressure, and more particularly to an improvement of the nozzle-mounting device in the stability of mounting of the suction nozzle on the nozzle holder.
2. Discussion of Related Art
Various types of nozzle-mounting device are known. JP-A-5-55796 discloses an example of the nozzle-mounting device, which uses sheet springs for mounting a suction nozzle on a nozzle holder. The sheet springs are fixed on the body of the nozzle holder, at respective positions that are spaced from each other in the radial direction of the nozzle holder. Each of the sheet springs is fixed so as to extend downward in the axial direction of the nozzle holder, and includes a holding portion at a relatively low part thereof and a guiding portion extending from the holding portion. The holding portion is inclined with respect to the axial direction, so as to extend toward the axis of rotation of the nozzle holder, while the guiding portion is inclined so as to extend away from the axis of rotation of the nozzle holder. The body of the nozzle holder is further provided with a spring for biasing the suction nozzle in the downward direction.
In the nozzle-mounting device disclosed in the above-identified publication, the body of the suction nozzle includes a fitting portion to be fitted in the body of the nozzle holder. The fitting portion takes the form of a cylinder which is closed and open at the respective opposite ends. The fitting portion has, at its open end, two guide surfaces formed at respective two positions that are spaced apart from each other in the diametric direction, and two inclined surfaces extending from the lower ends of the guide surfaces. The guide surfaces are formed so as to extend in the radially outward directions such that the guide surfaces are parallel to the above-indicated guiding portions of the sheet springs. The inclined surfaces extend toward the axis of rotation of the suction nozzle, and are inclined in parallel with the above-indicated gripping portions of the sheet springs. The suction nozzle is mounted on the nozzle holder, with the fitting portion of the suction nozzle being fitted into the body of the nozzle holder while being guided at its guide surfaces by the guiding portions of the sheet springs, so as to cause elastic deformation of the two sheet springs in opposite directions away from each other. After the inclined surfaces have passed the guiding portions, the fitting portion is biased by the spring provided on the nozzle holder body, so that the inclined surfaces are brought into engagement with the gripping portions of the sheet springs, whereby the suction nozzle is mounted on the nozzle holder such that the suction nozzle is neither axially movable nor rotatable relative to the nozzle holder. The suction nozzle can be removed from the nozzle holder, by pulling the suction nozzle in a direction that permits the fitting portion to be moved out of the body of the nozzle holder. Thus, the use of the sheet springs permits easy mounting and removal of the suction nozzle on and from the nozzle holder, by simply moving the suction nozzle in the axial direction relative to the nozzle holder.
However, a clearance must be left between the fitting portion of the suction nozzle and the body of the nozzle holder, in order to allow fitting engagement of the fitting portion with the nozzle holder body. Thus, there exists a small radial gap between the nozzle holder and the suction nozzle. This radial gap deteriorates the stability of radial positioning of the suction nozzle relative to the nozzle holder, causing problems such as a low degree of accuracy of mounting of an electric component on a printed-wiring board when the electric component held by suction by the suction nozzle is mounted on the printed-wiring board.
It is therefore an object of the present invention to provide a nozzle-mounting device which permits stable mounting of the suction nozzle on the nozzle holder. The above object may be achieved according to any one of the following modes of the present invention, each of which is numbered like the appended claims and depends from the other mode or modes, where appropriate, to indicate and clarify possible combinations of elements or technical features. It is to be understood that the present invention is not limited to the technical features or any combinations thereof which will be described for illustrative purpose only. It is to be further understood that a plurality of elements or features included in any one of the following modes of the invention are not necessarily provided all together, and that the invention may be embodied without some of the elements or features described with respect to the same mode.
(1) A nozzle-mounting device for removably mounting, on a nozzle holder, a suction nozzle for holding an electric component by suction under a negative pressure, the nozzle-mounting device is characterized in that:
the nozzle holder includes a first fitting portion and a second fitting portion which respectively have an inner circumferential surface and an outer circumferential surface and which are arranged to effect a fitting engagement with each other at the inner and outer circumferential surfaces, while the suction nozzle includes the other of the first and second fitting portions;
one of the first and second fitting portions is provided with a first abutting portion located at an axially intermediate portion of mutually fitting parts of the inner and outer circumferential surfaces, while the other of the first and second fitting portions is provided with a second abutting portion which is arranged to be brought into abutting contact with the first abutting portion in a direction intersecting axes of the first and second fitting portions; and
a pressing device is provided to force the inner and outer circumferential surfaces against each other by abutting contact of the first abutting portion with the second abutting portion.
Where both of the first and second abutting portions have abutting surfaces (flat or curved surfaces), the direction of the abutting contact of the first and second abutting portions with each other is normal to the abutting surfaces. Where one of the first and second abutting portions has an abutting surface while the other abutting portion has an abutting corner or edge, the direction of the abutting contact is normal to the abutting surface of the above-indicated one of the two abutting portions. The xe2x80x9cfirst abutting portion located at an axially intermediate portion of mutually fitting parts of the inner and outer circumferential surfacesxe2x80x9d may be interpreted to mean that the first abutting portion is located so that a force for forcing the inner and outer circumferential surfaces against each other acts on the axially intermediate portion of the mutually fitting parts of those circumferential surfaces.
For fitting engagement of the inner and outer circumferential surfaces of the first and second fitting portions, it is essential to provide a certain amount of clearance or gap (hereinafter referred to as xe2x80x9cfitting clearancexe2x80x9d) between the inner and outer circumferential surfaces. This fitting clearance is zeroed at a circumferential position of the inner and outer circumferential surfaces at which these circumferential surfaces are forced against each other by application of a force to one of the first and second fitting portions in a direction that intersects the axes of the fitting portions. Further, the application of the force in the direction intersecting the axes of the fitting portions to the first abutting portion located at the axially intermediate portion of the mutually engaging parts of the circumferential surfaces causes close pressing contact of the inner and outer circumferential surfaces with each other on the opposite sides of the axially intermediate portion, that is, along the entire length of the mutually engaging parts, so that an inclination of the axes of the first and second fitting portions with respect to each other can be prevented. Accordingly, a predetermined relative position of the first and second fitting portions in the radial direction is established by the abutting contact of the first and second abutting portions with each other, so that a predetermined relative position of the suction nozzle and the nozzle holder in the radial direction is established, even in the presence of the fitting clearance between the inner and outer circumferential surfaces. Thus, the suction nozzle can be mounted on the nozzle holder with a high degree of stability. The suction nozzle can be positioned in the radial direction with a high degree of positioning accuracy, as if the fitting clearance did not exist, as long as the eccentricity of the suction nozzle with respect to the nozzle holder due to the pressing contact of the inner and outer circumferential surfaces at one circumferential position is taken into account when the suction nozzle is positioned.
Each of the inner and outer circumferential surfaces is typically one cylindrical surface having a constant diameter. However, at least one of the inner and outer circumferential surfaces may have an axially intermediate recessed portion at which the inner and outer circumferential surfaces do not contact each other. In this case, the inner and outer circumferential surfaces are forced against each other along a generating line thereof, except at the axially intermediate recessed portion. Alternatively, each of the inner and outer circumferential surfaces may consist of a plurality of axial portions having different diameters, which are formed to permit the first and second fitting portions to eventually effect the fitting engagement with each other. In this case, the inner and outer circumferential surfaces are eventually forced against each other, along each of generating lines of the respective sets of axial portions of the first and second fitting portions which have the respective different diameters.
The pressing device may include: the first abutting portion fixedly provided on one of the first and second fitting portions; an abutting member functioning as the second abutting portion; a holding device for holding the abutting member such that the abutting member is movable in the direction intersecting the axes of the first and second fitting portions; and a biasing device for biasing the abutting member in a direction toward the first abutting portion. Alternatively, the pressing device may include the first and second abutting portions, and a biasing device. In this case, the first and second abutting portions are arranged to effect the abutting contact with each other in a direction which is inclined with respect to a plane perpendicular to the axes of the first and second fitting portions. The biasing device is arranged bias the above-indicated one of the first and second fitting portions against the other fitting portion, in a direction which is parallel to the axes of the fitting portions and which causes the first and second abutting portions to effect the abutting contact with each other. In either of the two cases indicated above, the second abutting portion functions to force one of the first and second fitting portions against the other in the radial direction so that the two fitting portions are eccentric with respect to each other, with the fitting clearance being zeroed at one circumferential position of the two fitting portions.
Where the first and second abutting portions are arranged to effect the abutting contact with each other in the direction inclined with respect to the plane perpendicular to the axes of the first and second fitting portions, the suction nozzle and the nozzle holder are positioned relative to each other in the axial direction, concurrently with the relative positioning in the radial direction. However, the relative positioning of the suction nozzle and the nozzle holder in the axial may be effected before or after the relative positioning in the radial direction.
(2) A nozzle-mounting device according to the above mode (1), wherein the second abutting portion includes a movable member supported by the nozzle holder such that the movable member is movable relative to the nozzle holder, and the pressing device includes a biasing device which biases the movable member in a direction for abutting contact with the first abutting portion, the nozzle holder being provided with a movable-member supporting device which movably supports the movable member.
For example, the biasing device includes an elastic member disposed between the movable member and the nozzle holder.
In the above mode (2) of the invention, the second abutting portion may be pressed onto the first abutting portion under a biasing action of the biasing device, for example, so that the inner and outer circumferential surfaces of the first and second fitting portions are forced against each other.
(3) A nozzle-mounting device according to the above mode (2), wherein said movable member is a pivotable member pivotable about a pivot axis thereof, and the biasing device includes an elastic member which acts on a portion of the pivotable member spaced from the pivot axis, to apply a pivoting torque to the pivotable member.
(4) A nozzle-mounting device according to any one of the above modes (1)-(3), wherein the first and second abutting portions are arranged to effect the abutting contact with each other on opposite sides of a plane which is parallel to the direction of the abutting contact and which includes the axes of the first and second fitting portions.
The directions of the abutting contact of the first and second abutting portions on the opposite sides of the plane including the axes of the first and second fitting portions are desirably parallel to each other as viewed in a plane perpendicular to the axes of the first and second fitting portions. However, those directions of the abutting contact may not be parallel to each other, but must not pass the axes of the first and second fitting portions. The direction of the abutting contact of the first and second abutting portions in general is determined by an average of the above-indicated two directions of the abutting contact on the opposite sides of the plane including the axes of the fitting portions.
In the above mode (4) of the invention, the abutting contact of the first and second abutting portions on the opposite sides of the plane parallel to the direction of the abutting contact and including the axes of the first and second fitting portions prevents rotation of the first and second fitting portions relative to each other. If the relative angular position of the first and second fitting portions upon fitting engagement therebetween is such that the first and second abutting portions initially contact each other on only one of the opposite sides of the above-indicated plane, an angular moment or torque is applied to one of the first and second fitting portions so that the two fitting portions are rotated relative to each other until the first and second abutting portions eventually contact each other on the opposite sides of the above-indicated plane. Thus, the rotation of the first and second fitting portions relative to each other is eventually prevented by the abutting contact of the first and second abutting portions on the opposite sides of the above-indicated plane. Where the second abutting portion is a substantially rigid member, in particular, a predetermined angular position of the first and second fitting portions relative to each other is established by the abutting contact of the first and second abutting portions, so that a predetermined relative angular position of the suction nozzle and the nozzle holder is established by the abutting contact of the two abutting portions.
The abutting contact of the first and second abutting portions causes the first and second fitting portions to effect the fitting engagement with their inner and outer circumferential surfaces being forced against each other at one circumferential position, along a generating line of the circumferential surfaces, which generating line lies on the above-indicated plane. Namely, the abutting contact takes plane on the opposite sides of the generating line as viewed in the circumferential direction of the fitting portions. The second abutting portion not only functions, as described before, to zero the fitting clearance at the above-indicated one circumferential position, for thereby causing eccentricity of the two fitting portions, but also functions to prevent the rotation of the two fitting portions relative to each other.
(5) A nozzle-mounting device according to any one of the above modes (1)-(4), wherein the first and second abutting portions are arranged to effect the abutting contact with each other in a direction which is inclined with respect to a plane perpendicular to the axes of the first and second fitting portions, such that the abutting contact causes an axial force to be generated for forcing the suction nozzle and the nozzle holder toward each other in an axial direction thereof.
In the above mode (5) of the invention, the abutting contact of the first and second abutting portions causes one of the first and second fitting portions against the other in the radial direction, and generates the axial force to be applied to the above-indicted one fitting portion, for thereby forcing the suction nozzle and the nozzle holder toward each other in the axial direction. This axial force prevents the removal of the suction nozzle from the nozzle holder. Where the second abutting portion includes a movable member, however, the suction nozzle is permitted to be removed from the nozzle holder by application of a sufficiently large force to the suction force in a direction away from the nozzle holder, since the movable member is moved against a biasing force of the biasing device away from the first abutting portion. Therefore, the suction nozzle can be removed from the nozzle holder, when needed.
Thus, the first and second abutting portions arranged to effect the abutting contact with each other in the direction inclined with the plane perpendicular to the axes of the first and second fitting portions serve as a nozzle-holding device for holding the suction nozzle on the nozzle holder. This nozzle-holding device arranged to force the suction nozzle and the nozzle holder toward each other in the axial direction is effective to reduce the deterioration of the elastic member of the biasing device used in the pressing device, as described above with respect to the above form (1) of the invention, as compared with a conventional nozzle-holding device using only sheet springs. Accordingly, the expected service life of the present nozzle-mounting device can be prolonged.
(6) A nozzle-mounting device according to any one of the above modes (2)-(5), wherein the pressing device includes a stop operable to define a maximum amount of movement of the movable member of the second abutting portion in a direction toward the first abutting portion.
When the movable member of the second abutting portion has been fully moved to a position defined by the stop, for abutting contact with the first abutting portion, not only a further movement of the movable member toward the first abutting portion, but also a movement of the movable member in a direction away from the first abutting portion are inhibited, unless a force larger than the biasing force of the biasing device is applied to the movable member in the direction away from the first abutting portion. Therefore, the movable member placed in the position defined by the stop functions as if it were a stationary member.
(7) A nozzle-mounting device according to any one of the above modes (2)-(7), wherein a second biasing device which biases the suction nozzle and the nozzle holder in the axial direction away from each other is provided in addition to the biasing device of the pressing device provided as a first biasing device.
When a biasing force larger than the biasing force of the second biasing device is applied to the suction nozzle in a direction opposite to the direction of the biasing force of the second biasing device, the suction nozzle is moved toward the nozzle holder, with elastic deformation of the second biasing device. This elastic deformation is effective to alleviate a shock to be generated upon abutting contact of the suction nozzle with the electric component, or upon abutting contact of the electric component held by the suction nozzle with a printed-wiring board when the electric component is mounted on the printed-wiring board. The second biasing device not only functions to permit the suction nozzle and the nozzle holder to be moved relative to each other in the axial direction, but also has a cushioning function for reducing the shock indicated above. The second biasing device may cooperate with other elements to perform another function, as described below with respect to the following mode (8) of this invention, for illustrative purpose only.
(8) A nozzle-mounting device according to the above mode (5), wherein the pressing device includes:
a movable-member supporting device which supports a movable member of the second abutting portion such that the movable member is movable in the direction intersecting the axes of the first and second fitting portions;
a first biasing device which biases the movable member in a direction for abutting contact with the first abutting portion;
a stop operable to define a maximum amount of movement of the movable member by a biasing force of the first biasing device in a direction toward the first abutting portion; and
a second biasing device which biases the suction nozzle and the nozzle holder in the axial direction away from each other,
and wherein the abutting contact of the movable member of the second abutting portion and the first abutting portion with each other in the direction inclined with respect to the plane generates an axial force which acts on the suction nozzle in the axial direction toward the nozzle holder.
While the movable member is placed in the fully moved position defined by the stop, the first biasing device biasing the movable member does not function to force the first and second fitting portions against each other through the movable member. On the other hand, the second biasing device biases the suction nozzle and the nozzle holder in the axial direction away from each other, so that the movable member in abutting contact with the first abutting portion. Since the direction of this abutting contact is inclined with respect to the plane perpendicular to the axes of the fitting portions, the abutting contact causes the first and second fitting portions to be forced against each other in the radial direction, owing to the inclination of the direction of the abutting contact. As a result, the predetermined relative position of the suction nozzle and the nozzle holder relative to each other in the radial direction is established by the abutting contact, as described above. At the same time, the abutting contact of the movable member and the first abutting portion with each other prevents the movement of the suction nozzle and the nozzle holder in the axial direction away from each other, so that the predetermined position of the suction nozzle and the nozzle holder relative to each other in the axial direction is also established. In the nozzle-mounting device according to the present mode (8) has the feature according to the above feature (4), the predetermined angular position of the suction nozzle and the nozzle holder relative to each other is also established.
(9) A nozzle-mounting device according to any one of the above modes (1)-(8), wherein the suction nozzle includes the first fitting portion having the inner circumferential surface, while the nozzle holder includes the second fitting portion having the outer circumferential surface.
(10) A nozzle-mounting device according to the above mode (9), wherein the first fitting portion of the suction nozzle is provided with two first abutting portions located on opposite sides of a plane which is parallel to the direction of the abutting contact and which includes the axis of the first fitting portion, while the second fitting portion is provided with two second abutting portions for abutting contact with the two first abutting portions.
The direction of the abutting contact has been discussed above with respect to the above form (4).
In the above mode (10) of this invention, rotation of the suction nozzle relative to the nozzle holder is prevented by the abutting contact of the two first abutting portions with the respective two second abutting portions.
(11) A nozzle-mounting device according to the above mode (10), wherein the two first abutting portions consist of two projecting pins which extend from an outer circumferential surface of the first fitting portion in opposite directions such that the two projecting pins are coaxial with each other.
The two projecting pins are disposed so as to lie on a plane perpendicular to the axis of the first fitting portion. The two projecting pins may be two separate pins. Alternatively opposite end portions of a single pin may function as the two projecting pins.
(12) A nozzle-mounting device according to any one of the above modes (1)-(8), wherein the suction nozzle includes the second fitting portion having the outer circumferential surface, while the nozzle holder includes the first fitting portion having the inner circumferential surface.
(13) A nozzle-mounting device according to the above mode (12), wherein the first abutting portion provided on the second fitting portion of the suction nozzle is formed on the outer circumferential surface so as to extend in a direction which is inclined with respect to a plane perpendicular to the axis of the second fitting portion, such that the abutting contact of the first abutting portion with the second abutting portion generates an axial force which acts on the suction nozzle in an axial direction toward the nozzle holder, and the first fitting portion of the nozzle holder has an opening which permits the second abutting portion to be brought into abutting contact with the first abutting portion.
The second abutting portion is arranged to be brought into abutting contact with the first abutting portion, while extending through the opening formed through the first fitting portion. Owing to the inclination of the first abutting portion with respect to the plane perpendicular to the axis of the second fitting portion, the abutting contact of the second abutting portion with the first abutting portion generates the axial force for forcing the first and second fitting portions against each other in the axial direction, to there by force the suction nozzle and the nozzle holder toward each other in the axial direction.
(14) A nozzle-mounting device according to the above mode (13), wherein the first abutting portion is a side surface of a cutout formed in the outer circumferential surface of the second fitting portion.
(15) A nozzle-mounting device according to the above mode (10) or (13), wherein the second abutting portion includes at least one roller rotatable about an axis perpendicular to the axes of the first and second fitting portions.
The at least one roller of the second abutting portion rolls on the first abutting portion when each roller comes into abutting contact with the first abutting portion or moves apart from the first abutting portion. Thus, the abutting contact of the first and second abutting portions with each other takes place with a rolling friction rather than a sliding friction, permitting a smooth operation of the first and second abutting portions and a reduced amount of wear of these abutting portions.
(16) A nozzle-mounting device according to any one of the above modes (1))-(15), wherein a low-friction coating having a lower friction coefficient than the first and second fitting portions is formed on at least one of the inner and outer circumferential surfaces of the first and second fitting portions.
In the above mode (16) of this invention, the first and second fitting portions can smoothly slide on each other, facilitating relative rotation and axial movement of the two fitting portions. Where the second biasing device biasing the suction nozzle and the nozzle holder in the axial direction away from each other as described above with respect to the above mode (7), for instance, the cushioning function of the second biasing device is effectively performed to prevent damaging of the electric component and/or damaging or bending of the suction nozzle upon sucking of the electric component by the suction nozzle. Where the first and second abutting portions are arranged to effect the abutting contact with each other on the opposite sides of the plane parallel to the direction of the abutting contact and including the axes of the fitting portions, as described above with respect to the above mode (4), for example, the abutting contact of the first and second abutting portions causes smooth rotation of the first and second fitting portions relative to each other, so as to establish the predetermined relative angular position therebetween.
The low-friction coating may be formed on both of the inner and outer circumferential surfaces, or only one of these circumferential surfaces. Where the low-friction coating is provided on only one of the two circumferential surfaces, the low-friction coating is preferably provided on the circumferential surface of the fitting portion of the suction nozzle. In this case, the circumferential surface of the fitting portion of the nozzle holder is preferably hardened, annealed and ground. In this respect, it is noted that the same nozzle holder is used for a plurality of suction nozzles each of which is repeatedly mounted on and removed from the nozzle holder, so that the nozzle holder is required to have a high degree of durability.